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SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'b278f942c0492ed2a099ad4c5c33f4d9002682268ae97b453ac11999e75ef183' 
  AND token = 'csauiOIquCe46rq3YzixD6oNaXvRL31tEFncdi+8Mgg=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00024

JSON explain

{
  "query_block": {
    "select_id": 1,
    "message": "no matching row in const table"
  }
}